The invention relates to a method and apparatus for preventing fluid solidification in an aperture, and, more particularly, to the utilization of an expansion member for positioning in a normally fluid filled cavity to prevent the fluid solidification therein.
For certain applications, such as drilling explorations in frozen Artic regions, it is desirable to install monitoring instrumentation in subfreezing areas. In particular, it has been shown to be advantageous to install instrumentation hardware including supporting struts and cables in floating ice sheets in order to monitor subsurface current characteristics such as water speed and direction as well as movement of the ice sheets themselves. Such monitoring has proven to be helpful in charting and evaluating Artic conditions which would affect various operations therein.
Ice sheets can vary substantially in thickness from the time that equipment may be installed to the time of its retrieval. The usual method of installing monitoring equipment in such an unstable supporting environment is through the utilization of an elongated, narrow surface support strut or cable with the select instrument package affixed to the lower end thereof. The strut is lowered into a generally circular hole bored through the ice to the water therebeneath. The top of the strut is then secured on the surface of the ice. The diameter of the bore at the time of installation is of sufficient size for clearance of the instrument package lowered therethrough. However, during the intervening time period between installation and retrieval, the ice section will generally have increased in thickness and the normally water filled bore will have solidified around the relatively narrow support strut or cable. Such an occurrence severely isolates the generally expensive instrument package in the water therebeneath creating a formidable retrieval problem.
Retrieval of the monitoring equipment from an ice pack is both time consuming and expensive and is unnecessarily complicated by a solidly encased supporting structure. Such a condition is oftentimes dealt with by boring a second hole adjacent to the solidified first, wherein the strut may be forced through the wall thereof to allow retrieval through the second hole. Although effective in recovering the monitoring equipment, such efforts are both disadvantageously expensive and time consuming. The locale of the ice installation generally necessitates the use of a helicopter for transportation and construction purposes. A helicopter is exceedingly expensive on an hourly basis, and time spent for boring a second hole singularly useful for the removal of a strut in an adjacent hole is frequently deemed uneconomical. In some such situations, the equipment is thus abandoned. At other times, however, the immediate need of the equipment itself for critical diagnostic purposes or use at other locations necessitates this expensive and cumbersome retrieval process.
It would be an advantage therefore, to avoid the problems of prior art methods and apparatus for installing equipment and related hardware in ice, to provide an inflatable bladder for interpositioning between the hardware and the walls of the ice wherein ice build-up normally occurs. The invention of the present method and apparatus is provided just for such a purpose. The equipment retrieval technique provided therewith is much more efficient than that of the method of allowing the equipment to be solidified within the ice in which it is originally freely positioned. Additionally, all of the equipment including apparatus such as an inflatable bladder disposed within the ice may be recovered quickly for subsequent use in a much more efficient and economical manner.